Why caching reduces response latency in NestJS - Performance Evidence

Performance: Why caching reduces response latency

HIGH IMPACT

Caching reduces the time it takes for the server to respond by avoiding repeated heavy computations or database calls.

Serving frequently requested data in a NestJS API

NestJS

private cache = new Map<string, User>();

async getUserData(userId: string) {
  if (this.cache.has(userId)) {
    return this.cache.get(userId);
  }
  const user = await this.database.findUserById(userId);
  this.cache.set(userId, user);
  return user;
}

Returns cached data instantly for repeated requests, reducing server work.

📈 Performance GainResponse time drops to under 5ms for cached requests, reducing server load

Serving frequently requested data in a NestJS API

NestJS

async getUserData(userId: string) {
  return await this.database.findUserById(userId);
}

Every request hits the database causing slow responses and high server load.

📉 Performance CostBlocks response for 50-200ms per request depending on DB speed

Performance Comparison

Pattern	Server Processing	Database Queries	Response Time	Verdict
No caching	High CPU and I/O	One query per request	50-200ms	[X] Bad
With caching	Minimal CPU	Zero queries on cache hit	Under 5ms	[OK] Good

Rendering Pipeline

When caching is used, the server skips database queries and complex logic, sending data immediately. This reduces backend processing time and speeds up the network response.

→Server Processing

→Network Transfer

⚠️ BottleneckServer Processing (database queries and computations)

Core Web Vital Affected

INP

Caching reduces the time it takes for the server to respond by avoiding repeated heavy computations or database calls.

Optimization Tips

1Cache data that is expensive to compute or fetch to reduce server response time.

2Use in-memory or fast-access storage for caching to maximize speed gains.

3Ensure cache invalidation strategies to keep data fresh without sacrificing performance.

Performance Quiz - 3 Questions

How does caching reduce response latency in a NestJS API?

A By avoiding repeated database queries and returning stored data quickly

B By increasing the number of database queries to speed up data retrieval

C By delaying the response to batch multiple requests together

D By compressing the response data to reduce size

DevTools: Network

How to check: Open DevTools, go to Network tab, make repeated API calls and observe response times.

What to look for: Cached responses show much lower latency and faster load times compared to uncached ones.